1. Field of the Invention
The present invention relates to the use of a secret quantity coming from an integrated circuit or from an electronic unit containing such a circuit. For example, the present invention relates to the use of such a secret quantity by programs such as an encryption key, as a secret quantity of an integrated circuit identification or authentication process. The present invention more specifically relates to the use of a digital identifier of an integrated circuit chip derived from a physical parameter network linked to the manufacturing of the integrated circuit chip.
2. Discussion of the Related Art
The use of an identifier derived from a physical parameter network, for example, to authenticate an integrated circuit chip or to code a datum that it provides, is more and more appreciated since this enables using a binary word hidden or embedded in the integrated circuit without permanently storing it in a storage element that could be pirated. The system reliability against possible frauds is thus improved. Further, the use of a physical parameter network enables obtaining digital identifiers distinct from one another for different integrated circuit chips originating from a given manufacturing.
Generally, the digital identifier of the integrated circuit is provided to the outside of the circuit after having possibly been coded or scrambled to be transmitted to a remote system. The latter exploits the word that it receives, generally without having to know the identifier.
An example of application of the present invention relates to the field of smart cards used for financial transactions from count units, prepaid or not, be the transmission with or without contact with the smart card reader.
Another example of application relates to data transmission systems using a personalized decoder on the user side. In such a case, the decoder may include an authentication circuit exploiting an identifier derived from a physical parameter network of an integrated circuit that it contains. By analogy with smart card readers used in payment systems, this amounts to combining a reader with its smart card at the user level, the authentication remaining made by a system different from the reader.
A disadvantage of the use of an integrated circuit identifier derived from a physical parameter network is linked to its individual and immovable character.
Thus, in the case where a pirate succeeds in pirating the identifier or a digital word (authentication amount or coding key) containing this identifier, there is no other solution than changing the integrated circuit. Indeed, from the moment that the identifier is suspected to have been pirated, it is desirable, in secure applications, to no longer use this identifier. This phenomenon is generally known as the revocation of a coding key or of an authenticator, or more generally of a secret quantity.
The absence of any solution to the revocation of a key or of a secret quantity based on the use of a physical parameter network of an integrated circuit presently limits the use of these identifiers which are, for many other purposes, very advantageous.